Firefighters battling wildfires in Australia’s most populous state attempted to make headway Thursday amid favourable conditions, before an “extreme heatwave” hits embattled areas on the weekend.

Thousands of firefighters in New South Wales took advantage of cooler weather and continued to strengthen containment lines. More than 70 fires, however, were still burning across the state with areas in the south coast currently at the “watch and act” level issued by fire services.

About 5 million hectares of land have burned nationwide over the past few months, with nine people killed and more than 950 homes destroyed. New South Wales has received the brunt of the damage, with around 850 homes razed in the state.

Bureau of Meteorology forecaster Rose Barr said a heatwave was currently building in southern parts of New South Wales before worsening on the weekend.

“Some areas are forecast to reach extreme heatwave conditions,” she said. “With the increasing heat and winds, the fire danger will worsen into the new week, with Monday and Tuesday most likely to be the most significant fire weather days.” Fire danger ratings remained very high in north-western New South Wales, and high in Sydney.Meanwhile, South Australian firefighters Thursday were battling wildfires in Adelaide Hills, which has been downgraded to the “advice” level.